This invention relates to antigenic modification of polypeptides. More specifically, this invention relates to processes for modifying polypeptides which are not substantially immunogenic to the immune system of mammals so as to make the modified polypeptides more immunogenic. The invention also relates to the modified polypeptides so produced, to vaccines containing such modified polypeptides, and for processes for affecting in various ways the metabolism of animals using such modified peptides and vaccines.
It is well known that antibodies are generated in humans and in other animals in response to the presence of foreign antigens. It is also known to confer immunity on an animal by administering an antibody formed elsewhere. For instance, patents to Michaelson (U.S. Pat. No. 3,553,317), Friedheim (U.S. Pat. No. 2,388,260), Reusser (U.S. Pat. No. 3,317,400) and Peterson (U.S. Pat. No. 3,376,198) relate to production of antibodies, which when injected into an animal of a different species or into a human being cause passive immunization. In patents to Fell (U.S. Pat. Nos. 2,301,532 and 2,372,066), the patentee refers to active immunization using modified histamine in such animals as horses, cows, etc. In a paper by R. G. Edwards in the British Medical Journal, Vol. 26, pages 72 to 78, published in 1970, on "Immunology of Conception and Pregnancy", he surveys the literature regarding the possibilities of utilizing immunological methods to influence or control fertility, surveying first production of antibodies against testes or spermatozoa. Much of the literature surveyed is directed to the production of foreign antibodies which are injected into the subject (passive immunization).
Hormone antibodies have been studied for a long time and the effect of specific antisera have been recorded for many years. It is known that administration of certain antibodies during pregnancy can suppress implantation or cause fetal resorption. Several different approaches have been tried ranging from the induction of near permanent infertility in the case of agglutination of spermatozoa in the male to the disturbance of a single pregnancy by passive immunization with antibodies.
There are serious limitations to the use of passive immunization procedures for human therapy. Since the antibodies are practically produced only in non-human animals, the repeated injection of animal proteins into humans is known to produce serious reaction in many individuals.
British Patent Specification No. 1,058,828 discloses that small molecules, referred to as "serological determinant peptides", can be coupled to large protein molecules, such as cattle albumin, and the resultant conjugate then may be injected into animals for antibody production. The document lists proteins from which the serologically determinant peptides may be isolated prior to being used in the process taught, the collection including viruses and bacteria whose surface component has the characteristics of a protein, toxins and hormones having protein structure and enzymes. No specific hormone is named in the document and no utility of anti-hormone immunization is described. The patent specification references a publication entitled: "The Specificity of Serological Reactions", Dover Publications, Inc., New York, 1962, Chapter V, "Artificial Conjugated Antigens" by K. Landsteiner. This publication outlines various chemical methods and applies them passively to bind various toxic substances in the blood such as arsenic. Thyroxine data provided in the publication suggests that such methods may be applied to hormones without indicating the therapeutic application, the publication teaching that specific antibodies may be formed to the small molecules and these antibodies are capable of neutralizing the biological action of a large protein from which the small peptide was a part.
Recently it has been discovered that doses of certain steroids consisting of synthetic non-protein hormones ("The Pill") when administered at stated intervals usually confer protection against pregnancy for a short time (possibly a month). This medication has sometimes been found to create undesirable side effects in creating undesirable metabolic changes and sometimes changes in the blood clotting mechanisms. Moreover, the effect of each dose is of such short duration that often it is of limited application, particularly in remote areas to persons not readily instructed on proper and continuing use.
There is therefore a need for an effective safe method of creating a temporary but relatively one-time immunity against pregnancy which does not have serious side effects. There is also a need for an effective safe method of terminating a pregnancy soon after conception which does not have serious harmful side effects. Such need may be met by the neutralization of a reproductive protein which is necessary for the normal events of conception and/or gestation.
There is also a need for a means for control of various disease states or maladies caused or influenced by unusual excesses of certain polypeptides such as gastrin, angiotension II, or somatomedian. It is believed that this invention meets this need safely and effectively.
There are also other medical needs which can be met by the present invention. It is well known to those skilled in the art of cancer treatment that certain cancers are highly resistant to the attack which would normally be made on the cancer by the immune system of a mammal in which the cancer is located. It is believed that this high resistance of certain cancers to attack by mammalian immune systems is due to the ability of the cancer to coat its external surface with materials which closely resemble certain materials endogenous to the animal in which the cancer is located, so that the animal's immune system does not detect the "foreign nature" of the cancer and hence is unable to attack it. The present invention may provide a mechanism by which the pseudo-endogenous material coating certain cancers can be stripped away, thereby facilitating attack on such cancers by the immune system of the animal in which the cancer is located.
One further use for the processes, compositions and therapeutic methods of the instant invention may be in dealing with diseases caused by agents which are not highly antigenic to mammalian immune systems. Although mammalian immune systems are extremely complex and extremely effective in dealing with most non-endogenous materials (such as bacteria and viruses) which find their way into the bodies of mammals, there are certain at least potentially dangerous non-endogenous materials which are not strongly antigenic to certain mammalian immune systems, and which thus do not provoke a sufficiently strong response from the immune system to avoid possible damage to the animal's body. The instant invention furnishes ways in which relatively non-antigenic, non-endogenous materials, for example viral proteins, can be synthetically modified to make them more strongly antigenic, thereby provoking the formation, in the body of animals, of relatively large quantities of antibodies to the non-endogenous materials, with consequent reduced risk of damage to the immune system if it thereafter is exposed to the non-endogenous materials.